Method of making a wound multi-ply paper tube



March 4, 1969 MCCLEERY B. CUNNINGHAM 3,

METHOD OF MAKING A WOUND MULTI-PLY PAPER TUBE Sheet of 4 Filed May 27, 1965 INVENTOR. MQCLEERY B. CUNNlNGHAM ATTORNEY March 4, 1969 MCCLEERY s. CUNNINGHAM 3,430,543

METHOD OF MAKING A WOUND MULTI-PLY PAPER TUBE Filed May 27, 1965 Sheet 2 of 4 fig-4 INVENTOR.

M CLEERY B. CUNNINGHAM .2 11 BY g, 4

ATTORNEY March 4, 1969 MCQLEERY B. CUNNINGHAM METHOD OF MAKING A WOUND MULTI-PLY PAPER TUBE Sheet Filed May 2'7, 1965 MECLEERY B. %N\NGHAM BY 1227 .l11'illll'llllllll.

ATTORNEY March 9 M CLEERY B. CUNNINGHAM 3,

METHOD OF MAKING A WOUND MULTI-PLY PAPER TUBE Sheet 4 of 4 Filed May 27, 1965 ATTORNEY United States Patent 3,430,543 METHOD OF MAKING A WOUND MULTI-PLY PAPER TUBE McCleery B. Cunningham, Hartsville, S.C., assignor to Sonoco Products Company, Hartsville, S.C., a corporation of South Carolina Filed May 27, 1965, Ser. No. 463,467

US. CI. 9394 Int. Cl. B31c 3/00, 13/00 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to paper tubes and more particularly to a method of making a wound multi-ply paper tube having a portion impregnated with a resinous material to produce a new and novel resulting product.

Paper tubes, both spirally and convolutely wound, are in common use today as carriers or cores for web material such as paper, cloth, fiber glass, plastic film and the like. When used for winding film material such as polyethylene, cellophane and the like, such cores are required to have a hard, smooth and cut-resistant surface in addition to having relatively high strength. As is well known, considerable wear and abrasion occurs on the peripheral surface of these cores, particularly when they are composed of paper. This wear considerably shortens the useful life of such cores so that they are generally discarded after a single use. It has been found that imperfections in the core surface would not only be damaging to the fragile film wound thereon, but irregularities in the surface are transmitted throughout all of the wraps or plies of film material wound thereon with a resultant deformation of the material. Furthermore, the severe stresses to which such cores are subjected during winding and handling are often in excess of that which such cores are capable of handling. While ordinary paper has qualities such as low cost and light weight which make it attractive for the manufacture of such cores, its relatively low strength and softness is a distinct disadvantage when it is used for such cores. It has been necessary to resort to the use of expensive materials other than paper such as metal, plastic and the like to obtain the desired core strength and core surface hardness.

Accordingly, a primary object of this invention is to provide a new and novel process for producing a plastic reinforced paper tube or core having a smooth, hard, cutresistant outer surface.

Another object of this invention is to provide a new and novel treated paper tube, the major portion of which is composed of ordinary paper which may be reused repeatedly in the winding of fragile web materials such as plastic film and the like without damaging such fragile materials.

A further object of this invention is to provide a new and novel process for impregnating a paper tube with a resinous material to provide a smooth, hard, cut-resistant outer surface on the tube.

A still further object of this invention is to provide a new and novel process for impregnating a portion of a paper tube with a self-curing resinous mixture which begins its self-curing action only after impregnation of the paper tube.

Still another object of this invention is to provide a new and novel process for impregnating only an outer layer of a paper tube with a resinous material in a manner such that substantially all of the advantages of a completely impregnated paper tube are obtained at a substantial reduction in cost, which permits the use of readily available material, and which process may be carried out in a simple and easy manner.

Another object of this invention is to provide a new and novel process for producing a spirally wound paper tube having one or more outer plies impregnated with a self-curing resinous mixture to provide a hard, smooth, cut-resistant outer surface on the tube and which permits the use of conventional spiral tube winding apparatus so that the entire tube may be produced continuously.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings.

The objects stated above and other related objects in this invention are accomplished by the provision of a composite multi-ply tubular member or core for winding web material which includes an ordinary paper tube of conventional multi-ply, convolutely or spirally wound construction. Paper which has been impregnated with a resinous mixture is wound on this paper tube to form a multiply outer layer. The resin in the outer layer is cured to provide a hard, smooth, cut and wear-resistant peripheral surface on the composite core. This multi-ply outer layer may be either convolutely or spirally wound on the paper tube and the paper forming this outer layer is preferably impregnated with a self-curing resinous mixture. The impregnation of this paper with a self-curing resinous mixture is preferably carried out by first impregnating the paper with a resin, preferably a polyester resin, and a catalyst for the resin and then subsequently impregnating the resin-catalyst impregnated paper with a mixture of the same resin and an accelerator for the resin. The outer layer is then covered with a layer of impervious release material and an outer wrap which are subsequently removed after curing to provide a finished tubular member or core. The well known chemical reaction between the resin, catalyst and accelerator cures the resin in the outer layer to form a composite core having an inner dry paper tube covered with a hard, smooth outer shell.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a side elevation view, partially cut away, of apparatus employed in the practice of the invention;

FIGURE 2 is a sectional view of the apparatus of FIGURE 1;

FIGURE 3 is a perspective view of a spirally wound paper tube which is incorporated in the composite core of the invention;

FIGURE 4 is an enlarged end view of the tube of FIG- URE 3;

FIGURE 5 is a perspective view similar to FIGURE 3 illustrating one step in the process of the invention;

FIGURE 6 is an enlarged end view of the tube of FIGURE 5;

FIGURE 7 is a view similar to FIGURE 5 illustrating another step in the process of the invention;

FIGURE 8 is an enlarged end view of the tube of FIG- URE 7;

FIGURE 9 is a view similar to FIGURE 7 showing a further step in the process of the invention;

FIGURE 10 is an enlarged end view of the tube of FIGURE 9 at the completion of the step of FIGURE 9;

FIGURE 11 is a perspective view of the composite core of the invention illustrating an additional operation which may be performed on the core;

FIGURE 12 is a plan view of another apapratus used in the practice of the invention to produce another embodiment .of the invention;

FIGURE 13 is an enlarged sectional view taken substantially along line 1313 of FIGURE 12 in the direction of the arrows;

FIGURE 14 is an enlarged sectional view of a composite core produced by the apparatus of FIGURE 12 at one stage of its manufacture; and,

7 FIGURE 15 is a perspective view of a finished composite core produced by the apparatus of FIGURE 12.

As generally illustrative of the invention, there is shown in FIGURES 1, 2 apparatus for producing one embodiment of the plastic impregnated composite tubular member or core of the invention. The core produced in the apparatus of FIGURES 1, 2 is identified generally in FIGURE 11 by the numeral 10 and comprises a multi-ply wound inner paper tube designated generally by the numeral 11 in FIGURE 3 and a hard multi-ply outer layer 12 of resin impregnated paper.

The apparatus of FIGURES 1, 2 comprises a first paper impregnating station designated generally by the numeral 13, a second impregnating station identified generally by the numeral 14 and a winding station identified generally by the numeral 15. A web 16 of paper pulled from a supply roll 17 supported on pedestal 18 is arranged to be advanced through a pair of pivotally mounted tension rolls 19 mounted on pedestals 20. The paper web 16 is subsequently advanced through the impregnating stations 13, 14 for impregnation with a suitable medium as will be described hereinafter. In the preferred embodiment of the invention, the paper impregnating medium is a self-curing resinous mixture of a resin, catalyst and an accelerator.

impregnating station 13 comprises a reservoir or trough 21 suitably supported on a stand 22. The trough 21 is arranged to contain a bath 23 of a paper impregnating material which in the illustrated embodiment comprises a thermosetting resin such as a polyester resin and a catalyst for the resin. As is well known, the resin and catalyst selected are of the type which do not react or set up at room temperature over a prolonged period of time so the bath 23 remains in the fluid condition. The bath 23 is supplied from a suitable resin-catalyst supply source such as a drum 24 which is connected to the trough 21 by means of a conduit 25 having a metering valve 26 located therein.

An impregnating or kiss roll 27 is partially immersed in the bath 23 and is rotatably mounted at each end in bearings (not shown) supported on the stand 22. The roll 27 is driven through a speed reducer 28 connected to a motor 29 which permits the speed of the roll to be controlled. A brake designated generally by the numeral 31 and preferably electrically operated by means such as a solenoid 32 is positioned on the stand 22 adjacent one end of the roll 27. The brake 31 is of the well known type and is provided with shoes 33 which move into braking engagement wtih the roll 27 under spring action or the like when the solenoid 32 is deenergized.

Idler rolls 35 are rotatably supported at each end on the stand 22 in bearing pedestals 36 and position the advancing paper web 16 so that it is maintained in contact with the peripheral surface of roll 27 as shown.

As the web 16 advances through impregnating station 13, it is directed upwardly in the direction of the arrows to a scraper roll 37. A brake designated generally by the numeral 38 is associated with the scraper roll 37 which is supported at each end in bearing pedestals 39 positioned on a stand 40. The brake 38 may also be electrically operated as shown by a solenoid 41.

The impregnating station 14 is generally similar to 4 the impregnating station 13 and comprises a trough or reservoir 42 which is connected to the lower reservoir 21 by means of a deflector plate 43 of sheet metal or the like. The plate 43 permits fluid dripping from the web 16 as it moves from trough 21 to trough 42 to be conducted back into the lower reservoir 21.

The reservoir 42 contains a bath 44 of a second impregnating fluid which comprises resin of the type employed in the lower bath 23 together with an accelerator for the resin. The resin and accelerator in the bath 44 are selected so as not to chemically react or set up at room temperature over a prolonged period of time and therefore the bath 44 remains fluid. A suitable supply source for the bath 44 such as a drum 46 is provided as shown and communicates with the trough 42 by means of a conduit 47 including a valve 48 to maintain the bath 44 at the desired level.

An impregnating roll 49 is provided at the station 14 which is driven by means such as a speed reducer 51 and a motor 52 connected thereto. The roll 49 is partially immersed in the bath 44 as shown and is suitably supported at each end in hearings or the like (not shown) positioned on the stand 40. An electrically operated brake designated generally by the numeral 53 and provided with a solenoid 54 and shoes 56 is associated with the roll 49 in a manner similar to the brake 31 for roll 27 and operates, when de-energized, to brake the roll 49.

The winding station 15 comprises generally a head 57 mounted on a stand 58. The head 57 includes rotatable clamping means for a paper tube such as spaced chucks 59 which can be moved into engagement with the ends of a paper tube of the type shown in FIGURE 3 and identified by the numeral 11. A handwheel 61 is provided for axially moving at least one of the chucks in the well known manner for clamping a tube 11 placed in the head 57. Means are provided for rotating the chucks 59 which include a motor 62 connected by means of a belt 63 to drive pulleys 64 in any well known manner.

A shelf or platform 66 is suitably supported on the stand 40 of the impregnating station 14 by posts 67 or the like which supports sheets 68 of release material used in the assembly of the core 10 of the invention. These sheets of release material may be glassine, cellophane, wax paper or the like treated, if desired, with material such as silicone to enhance its release properties which is impervious to the resinous mixture used in the practice of the invention as will be explained hereinafter.

As specifically illustrative of the practice of the novel process of the invention, the embodiment of FIGURES 1-11 is directed to the construction of the core 10 which is hereinafter referred to as the convolute-type core. The term convolute-type indicates that the impregnated paper plies with which the core 10 is formed are convolutely wound rather than spirally wound on the paper tube 11.

In order to form the core 10 with the apparatus of FIGURES 1, 2, a paper tube 11 shown in FIGURE 3 is provided, which in the preferred embodiment is a spirally wound multi-ply paper tube of conventional construction having a central bore 71 and a relatively thin side wall 72. As is well known, the tube 11 is formed by spirally winding in helically overlapping relationship a plurality of paper plies with adhesive therebetween. It should be understood that the tube 11 may be either spirally or convolutely wound, but is preferably spirally wound due to the less expensive construction in comparison with the convolutely wound tube.

The paper tube 11 is positioned in the head 57 of winding station 15 for axial rotation and the handwheel 61 is rotated to securely clamp the tube 11 between the chucks 59. After tube 11 is clamped in position, the paper web 16 is unrolled from the supply roll 17 and is advanced through the tension rolls 19 and over the impregnating roll 27 with the paper Web being held against the roll 27 by means of the guide rolls 35 as shown. The brake 38 is reapplied so that the roll 37 resumes the scraping operation on web 16. Preferably, the roll 27 is rotated by means of the motor 29 at a greater peripheral speed than the web 16 so as to impregnate the web thoroughly with the mixture of resin and catalyst in the bath 23.

The resin-catalyst impregnated web 16 is then advanced upwardly in the direction of the arrow over the scraper roll 37 which at this time is braked by the solenoid operated brake 38 to scrape off the excess resin-catalyst on the underside of the web. The web 16 is advanced over the surface of the impregnating roll 49 as shown so that the resin-catalyst impregnated paper web 16 is now impregnated with the resin-accelerator mixture in the bath 44. The roll 49 is also preferably driven at a selected peripheral speed greater than the web speed so as to thoroughly impregnate the web 16 with the mixture in the bath 44.

As a result of the kiss type roll 27, the scraping action of the roll 37 and the use of a kiss type roll 49, virtually none or only a negligible amount of resin and catalyst is carried into the bath 44 and the mixture in the bath 44 does not react or set up as would occur when all three ingredients namely, the resin, accelerator and catalyst, are mixed. Thus, the elimination of catalyst in bath 44 is accomplished satisfactorily With the novel arrangement of the invention. It should be understood that during the impregnating of the paper web 16, the solenoid brakes 31, 53 at the impregnating stations 13, 14 have been released so that the rolls 27, 49 can be driven by drive motors 29, 52, respectively.

Referring now to FIGURES 5, 6, the end of the impregnated paper web 16 advancing from the impregnating station 14 to the winding station is secured to the paper tube 11 by means such as gummed tape 73 preferably extending throughout the length of the tube.

The paper tube 11 is then rotated by energizing the drive motor 62 so as to wind the impregnated paper web 16 on the tube in a plurality of wraps to build up the multi-ply outer layer 12 on the tube as indicated in FIG- URES 7, 8. Any desired number of wraps of the impregnated paper Web 16 may be used in forming the outer layer 12 and by way of example, eight to twelve wraps have been found suitable. A very satisfactory core has been produced wherein paper tube 11 comprises at least 90% of the total thickness of the core 10 of the invention, but it should be understood that where greater strength is desired, the proportion of the total thickness of the core 10 formed by the outer layer 12 may be increased to the desired extent.

Just before the last few wraps of impregnated paper are wound on the tube 11, impregnation of the paper web 16 is interrupted by first braking impregnating roll 27. Impregnating roll 49 is subsequently braked when it is reached by the dry paper so that the paper web 16 advances over the surfaces of both rolls 27, 49 without impregnation and a length of dry paper begins on the web 16 at the end of the last wrap of impregnated paper laid on the tube 11. The interval between the braking of rolls 27, 49 is to permit the impregnated length of web 16 to receive the mixture from both baths 23, 44. The brake 38 on the scraper roll 37 is released so that when dry paper is advancing over the roll 37, the roll rotates freely.

Prior to beginning the wrapping of the last impregnated wrap on the paper tube 11, a sheet 68 of release material is removed from the platform 66 and placed manually as shown in FIGURE 7 on the impregnated paper web being wound on the tube 11. Rotation of the tube 11 is halted at this time to permit the application of this release material and as the underlying paper is impregnated, the release material adheres readily.

After application of the sheet 68 of release material, rotation of the tube 11 is resumed and the release material is wound up with the underlying paper web so as to completely cover the impregnated layer 12 with approximately one wrap of release material the length of which has been selected so as to meet this requirement. As a resalt of the braking of the rolls 27, 49 as previously explained and the interruption in the impregnation of the paper web 16, the impregnated portion of web 16 tenninates approximately at the trailing edge of the sheet 68 of release material and continued rotation of the paper tube 11 wraps the dry portion of paper web 16 over the sheet 68 of release material as shown in FIGURE 9. In this manner, a suitable number of Wrap of unimpregnated or dry paper are applied so as to serve as an outer wrap 76 for the multilayer structure shown in FIGURE 10.

When the end of the length of dry outer wrap 76 is reached, the rotation of the paper tube 11 is terminated and the paper web 16 severed transversely. The cut edge of the outer wrap 76 may then be suitably held in position using gummed tape or the like. It should be understood that prior to reaching the end of the length of the dry paper web during the wrapping of the outer wrap 76, brakes 31, 53 are released to resume impregnation of the paper web 1 6 and web 16 can be severed at the beginning of the impregnated web portion when the core 10 is completely wound and ready to be removed.

As the mixture of resin-catalyst-accelerator with which the paper web 16 has been impregnated is a self-curing mixture, the multilayer structure of FIGURE 10 comprising the paper tube 11, outer layer 12, release material 68 and outer Wrap 76 can now be removed from the tube forming station 15 and set aside to permit the outer layer 12 to cure and harden. The release material 68 retains the resinous mixture in the outer layer 12 and the outer dry wrap 76 holds the release material in confining relationship with the underlying outer layer 12.

Subsequent to the curing operation, the outer wrap 76 and release material 68 can then be out off to expose the hard outer layer 12 which is now provided with a smooth, out and wear-resistant outer surface. The portion of the impregnated paper web 16 forming the outer layer 12 terminates at the inner end of the release material 68 so that along this edge a cut is made to sever and remove all of the outer wrap 76 and release material 68. Thus an edge is formed along this out line which is identified in FIGURES 7, 8 by the numeral 77.

In order to eliminate the edge 77 and provide an absolutely smooth outer surface on the outer layer 12 of core 10, a grinding operation is preferably carried out on the exterior surface 78 of the finished core 10 as shown in FIGURE 11. This grinding or sanding operation can be carried out by any suitable means such as an abrasive belt 79 mounted on drive rolls 81 as shown. If desired, progressively finer belt surfaces can be used so as to improve the smoothness of the core surface 78. If desired, the surface 78 may be further smoothed by recoating the ground surface 78 with a polyester-catalyst-accelerator mixture and permitting this coat to cure and harden at room temperature which generally is a fairly rapid operation. As a final operation, the ground core surface 78 can be bufied with a belt composed of a material such as leather to obtain a smooth glossy finish.

The finished core 10 therefore comprises the inner paper tube 11 and the outer layer 12 which presents a smooth, hard cut and wear-resistant surface so desirable when such a core is used as a winding core for fragile film materials such as cellophane and the like. As explained above, the outer layer 12 need only be a minor portion of the overall core thickness as the paper tube 11 reinforces the core outer layer 12 to provide a core having both an unusually hard outer surface and high strength.

A wide variety of resinous materials may be used with success in impregnating the paper web 16 to form the outer layer 12. These resinous materials may be cured by the application of heat and/ or pressure and any resinous material which will cure to a hard, durable condition can be used. However, in the specific embodiment illustrated, a self-curing mixture including resin gives a highly desirable result and the novel feature of the two-component system utilizing the two impregnating stations 13, 14 has been found to produce outstanding results in the practice of the invention as the resinous mixture in the troughs at each impregnating station will not cure or harden and therefore have an indefinite pot life to give highly attractive commercial advantages.

Among the resinous materials suitable for use in such a two-component system, polyester resins have been found to be very satisfactory. Such polyester resins can be defined as the poly-condensation products of unsaturated acids such as maleic and fumaric with dihydroxy alcohols such as ethylene glycol cross linked with a vinyl monomer such as styrene. These polyester resins can be polymerized at room temperature with catalysts such as benzoyl peroxide, cyclohexanone peroxide or methyl ethyl ketone peroxide together with accelerators such as dimethyl aniline or cobalt naphthenate.

In the specific embodiment illustrated, the polyester resin and catalyst form the bath 23 of impregnating station 13 and a polyester resin and accelerator form the bath 44 of impregnating station 14. The mixture of the resin, catalyst and accelerator with which the paper web 16 is impregnated will spontaneously set up and cure to a solid mass within a time determined by the nature, amounts and proportions of the catalyst and accelerator, and the actual proportions of each ingredient in the mixture may be varied to obtain variation in the speed of this curing action.

In the operation of the invention using such a two-component system, highly desirable results have been obtained using a 3% benzoyl peroxide paste in the bath 23 and a dimethyl aniline in the bath 44. Monomeric styrene can be added to the system to decrease the viscosity to get improved penetration of the resin into the paper.

Other resins which may be suitable for such use in the invention include the so called epoxy or epichlorohydrinbisphenol type of resin.

Referring now to FIGURES 12l5, there is shown an apparatus for producing another embodiment of a composite core constructed in accordance with the invention. This core, identified in FIGURE by the numeral 80, is similar to the core 10 of FIGURES 11l, but has other characteristics which permit it to be produced in a more economical and continuous fashion. In the apparatus shown in FIGURES 12, 13, conventional spiral tube winding machinery is illustrated, which includes a mandrel 81 supported at one end in a head 82. A multi-ply tubular structure 83, as shown in FIGURE 14, is formed continuously on the mandrel 81 and is cut off into sections of predetermined length 83a by means of any suitable cutoff device designated generally by the numeral 84. The cutoff sections 83a include the cores 80 of the invention.

As is well known, a continuous belt 86 is employed with the mandrel 81, being wrapped around the mandrel as shown, which belt is driven by a set of capstans or pulleys 87. A preform or dry paper tube 88 corresponding to the paper tube 11 of FIGURE 3 is continuously formed on the mandrel 81 by spirally winding a plurality of paper plies 89 of paper drawn from rolls 91 supported on a creel 92. The inner and outer plies 89a, 8%, respectively, are wound dry with the intermediate plies 89 being advanced through a glue bath 93 so that all of the plies are adhesively joined together to form the tube 88 as it is rotated by the belt 86 against the surface of the mandrel.

It will be noted that the inner ply 89a is fed from a supply roll 91a on the opposite side of the mandrel 81 from the other plies and underneath rather than over the mandrel. This is to permit a suitable liquid lubricant such as wax to drip from a reservoir (not shown) onto the ply 89a.

As in the embodiment of FIGURES 1-11, paper impregnating stations designated generally by the numerals 94, 95 are provided for impregnating a plurality of plies 96 of paper advancing in the direction of the arrows from a suitable source of supply such as a creel (not shown).

As shown best in FIGURE 13, the impregnating station 94 comprises a trough 97 containing a bath 98 of resin and a catalyst for the resin and each of the paper plies 96 are advanced over guide bars 99 and through the bath 98 guided by bars 101.

Excess resin-catalyst on the plies 96 is scraped off by means of a scraper 102 of conventional construction suitably supported over the trough 97 and an inclined trough extension 9711. The scraper 102 includes scraper bars 103, each of which contact a ply 96 advancing thereover to scrape the excessive material from the plies and permit it to drip back into the bath '98.

The paper plies 96 impregnated with resin and catalyst then advance to the impregnating station 95 where they are moved over freely rotatable impregnating rolls 104 arranged in a vertically stacked relationship as shown in FIGURE 13 on a stand 106. Each of the rolls 104 is partially immersed in a bath 107 of resin and an accelerator for the resin as in the previous embodiment maintained in a trough 108. Pairs of guide rolls 109, 111, are suitably supported on opposite sides of each roll 104 to guide the paper plies 96 in the desired direction and maintain the paper plies 96 in contact with the rolls 104. Thus, the paper plies 96, which have previously been impregnated with resin and catalyst at the impregnating station 94 are now impregnated with resin and accelerator in station 95 so that a self-curing mixture is soaked into all of the paper plies 96.

The impregnated paper plies 96 are then wound spirally onto the paper tube 88 as shown in FIGURE 12 down from the belt 86 as the tube moves forwardly in the direction of the arrow P to form an outer layer 112 as shown in FIGURES 14, 15 corresponding to the outer layer 12 of the core 10 of FIGURE 11. A paper strip 113 of release material such as silicon coated glassine is unwound from a supply roll 114 and is spirally wound onto the impregnated outer layer 112 in a single ply as shown in FIGURE 12. The strip 113 acts to retain the resinous material in the layer 112 as in the embodiment of FIGURES 1-11.

In order to hold the strip of release material in spirally wrapped relationship with the underlying layer 112, a strip 116 of gummed paper is unwound from a supply roll 117 and is spirally wrapped over the ply of release paper strip 113. The gummed paper strip 116 is preferably moistened prior to winding by advancing the adhesively coated side of the gummed paper over suitably moistening means 118.

Thus, the multi-ply structure 83 continuously formed on the mandrel 81 and pulled therefrom comprises four concentric portions-the spirally wound paper tube 88, the impregnated layer 112, the release material 113 and the outer gum strip wrap 116 as shown clearly in FIG- URE 14.

As this continuously formed multi-ply structure 83 moves into the cutoff device 84, sections 83a of predetermined length are severed therefrom and these sections 83a can be stored for a brief period of time until the layer 112 cures and hardens. After the layer 112 has cured and hardened, the outer wrap 116 and release material 113 can then be cut away in a manner similar to the embodiment of FIGURES 1-11 to provide the core of FIGURE 15 having a hard, smooth cut and wear-resistant outer layer as has been previously described. Furthermore, this outer layer 112 is preferably ground and buffed also, if desired, to provide the smooth outer surface resired in the core produced in accordance with the invention.

With the novel construction of this invention, there has been provided a new and novel core for winding film material which core is characterized by outstanding crush strength and a surface having the desired degree of hardness, smoothness and resistance to wear so that the core serves ideally for winding readily deformable film material such as cellophane and the like. Due to the outstanding strength of the core of the invention brought about by ordinary paper and resin impregnated paper combined in an unusual manner, only a relatively thin outer layer of resin impregnated paper need be provided on the composite multi-ply core with an attendant savings of expensive materials. This outer layer may also be formed by resin impregnation of other materials to provide a wide variety of surface appearance and strength characteristics. The core of the invention may be produced using a number of novel processes disclosed herein and in particular the core may be produced by a single sepiral tube winding operation commonly employed in everyday practice. An outstanding feature of the invention is the use of a self-curing mixture for impregnating the outer layer in the core wherein components of the mixture are located in two reservoirs so that all of the components remain in a fluid condition and are combined during impregnation of the paper so that they do not begin to set up or cure before the paper is Wound into the core of the invention.

Having thus described the invention, what is claimed 1. A method of making a composite multi-ply tubular member comprising the steps of, spirally winding a plurality of plies of paper with adhesive therebetween to form a wound multi-ply paper tube, impregnating a plurality of plies of paper with a self-curing mixture comprising a resin, catalyst for said resin, and an accelerator for said resin, spirally winding said plurality of plies of impregnated paper on said paper tube to form an outer layer,

spirally winding at least one ply of release material around said outer layer to retain the self-curing resinous mixture in said outer layer, spirally winding at least one adhesively coated ply of paper on said ply of release material, all of said spiral winding operations being performed simultaneously, and permitting said outer layer to cure and solidify to thereby form a hard, wear-resistant outer surface on said tubular member which is exposed when said release material and adhesively coated ply are removed. 2. A method in accordance with claim 1 wherein said plurality of plies of paper is first impregnated with a mixture of said resin and catalyst and subsequently impregnated with a mixture of said resin and accelerator.

References Cited UNITED STATES PATENTS 3,247,869 4/ 1966 Boegershausen et a]. 156-195 XR 2,814,313 11/1957 Tate 156-190 XR 2,723,705 11/1955 Collins 156195 XR 2,751,936 6/ 1956 Dunlap et al.

FOREIGN PATENTS 1,153,607 8/1963 Germany.

PHILIP DIER, Primary Examiner.

US. Cl. X.R. 

